According to Localytics technology website, Sprint’s addition to the market barely affected AT&T.

“Looking at iPhone 4 distribution as a comparison, Sprint seems to have eroded more of Verizon’s market share than AT&T’s,” said Localytics.

Verizon entered the market strongly last year immediately grabbing 40 percent of iPhone users in half the time.

Sprint launched the 4S handset with unlimited data plans leading some experts to anticipate AT&T losing a bulk of the market share when Verizon is taking the hit.

Sprint holds 12 percent of the market share with the iPhone 4S while Verizon occupies the second place spot with 32 percent. AT&T continues to dominate with iPhone 4S sales occupying more than half the market with 56 percent, according to Localytics.

“A likely driver for these differences is the fact that AT&T can mine its existing base of iPhone users,” Localytics said. “Because all Verizon iPhone users are in the first year of their wireless contract, the cost of upgrading will be high.”

So, while Verizon continues to hold a large chunk of the iPhone 4 market, much of its users could not upgrade to the iPhone 4S due to high costs of obtaining a new phone shortly after buying an iPhone 4. The situation makes it difficult for Verizon to stake a claim in the market of the newest iPhone.

Sprint entered the arena and most likely snatched up those looking for a more appealing smartphone on a network that previously did not make the Apple product available.

New carriers selling the smartphone shifts the market considerably, and once the next iPhone drops in 2012, other carriers might also enter and create even different effects in iPhone sales.